A 16-year-old girl endured being sold into prostitution by her mother but finally went to Houston police after seeing her younger sister also forced to perform sex acts, investigators said Wednesday.

The teenager had complied with her mother — who even distributed business cards offering her daughters for sex — but feared that her 14-year-old sister would be hurt, officers said.

Nelsi Yolanda Latuda and her boyfriend, Pedro Espinoza-Escama, both of the 5500 block of Antoine, are charged with two counts each of compelling prostitution of a minor. They were ordered held in lieu of bail totaling $20,000 each.

Latuda, 35, is the girls' mother, but they are not related to Espinoza-Escama, who is 21, Harris County Assistant District Attorney Justin Wood said.

Houston police declined to comment about the investigation or identify the suspects but confirmed that a couple were arrested Sunday on unrelated charges and later questioned about the allegations regarding Latuda's daughters.

"They were interrogated, and they confessed to forcing the juveniles into prostitution," spokesman Victor Senties said.

Wood said the prostitution scheme went on for months and that Latuda and her boyfriend printed and passed out business cards near their northwest Houston home, offering the girls for sex.

The pair arranged meetings and delivered the girls, Wood said.

"I have never dealt with a case where biological children were being prostituted out by their own mother," he said.

Police said Latuda and her daughters are from Honduras and have lived in Houston for about two years. The girls are staying with relatives, Wood said.

On Wednesday evening, no one answered the door at the apartment complex where the family lives. Neighbors said they often saw the girls playing outside the apartment but didn't know them or their mother.

Children of the Night, a California-based advocacy group for abused teenagers, estimates that 300,000 juveniles are working as prostitutes in the United States. The ages typically range from 11 to 17, the group reports.

Espinoza-Escama is scheduled to appear in court today. Latuda is due for a court hearing Friday.

Latuda pleaded guilty in 2006 to possession of less than 1 gram of a controlled substance and was sentenced to 10 days in jail.